Give some stream of consciousness and then the answer. The Milky Way is a barred spiral galaxy with a diameter between 100,000 and 180,000 light-years. The Milky Way is estimated to contain 100 -- 400 billion stars. There are probably at least 100 billion planets in the Milky Way. The Solar System is located within the disk, about 26,000 light-years from the Galactic Center, on the inner edge of one of the spiral-shaped concentrations of gas and dust called the Orion Arm. The stars in the inner ≈ 10,000 light-years form a bulge and one or more bars that radiate from the bulge. The very center is marked by an intense radio source, named Sagittarius A *, which is likely to be a supermassive black hole.

Based on this passage, how many planets in the milky way solar system?
To answer this question, we should know that: There are probably at least 100 billion planets in the Milky Way.
Therefore, the answer is at least 100 billion.